Phoresis corresponds to the motion of a particle induced by an external field, say \(\Theta _\infty \) : typically an electric potential for electrophoresis, a solute concentration gradient for diffusiophoresis, or a temperature gradient for thermophoresis [1]}, [2]}.
The particle velocity is accordingly proportional to the gradient of the applied field, writing in the general form
\(v_P= \mu _P \times (-\nabla \Theta _\infty )\) 
